And with good reason, because financial advisers give a lot of lousy recommendations.

Mired in conventional wisdom and focused on the needs of their wealthier clients, even the most independent advisers chart paths that are simply impractical for the vast majority of Americans.

If you don’t have a lot to invest, they’re at best useless and at worst actually destructive to setting realistic goals of saving and investing over a lifetime.

Here are my choices for the four most useless pieces of financial advice from a not-very-useful industry.

1. Your biggest retirement risk is outliving your money, so put 60% to 70% of your assets in stock when you retire. This, the financial-services industry’s most widely held bit of groupthink, is so wrong-headed I don’t know where to start. But I’ll try.

Outliving your money is a risk in retirement. But it’s not the only risk and not even the most important one. Inflation, while quiescent now, could rear its head again. A stock market plunge just as you retire could reduce your income for years. And then there’s cognitive decline, which impairs the financial judgment of one half of Americans over 80.

Having 60% to 70% of your money in stock won’t reduce any of these risks; it likely would make things worse. (Remember all that panic selling during the financial crisis?) And it certainly wouldn’t solve the biggest retirement problem we face — not having enough to retire at all. What’s the financial-services industry’s answer to that? Putting 90% in stock to make up for lost time?

2. Wait until you’re 70 to claim Social Security benefits. The numbers appear to be on the advisers’ side here: If you start taking Social Security when you’re 70, you will earn an additional risk-free 8% a year beyond your full retirement age of 66 or 67. That could mean an extra $60,000 in lifetime benefits for a single retiree with average life expectancy, according to Bank of America Merrill Lynch
BAC, -1.38%
which, not surprisingly, endorses this strategy.

Unfortunately, you’ll probably have to live past 84 to break even. But more importantly, who has the money to do this? Unless they have tens of thousands of dollars in extra savings sitting around, how can the vast majority of people afford to live without collecting benefits for three or four years?

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